The present invention relates to a resin composition excellent in flame retardancy and preferred for environmental protection.
For flame-retardation of flammable synthetic resins, there have been generally employed flame-retardation methods such as addition of halogen-containing compounds and antimony trioxide, etc. However, these conventional flame-retardation methods are not desirable for environmental health and there is a demand to improve them in this respect.
On the other hand, for flame-retardation of polyphenylene ether resins or mixed resins thereof with styrene resins or polycarbonate resins or mixed resins thereof with styrene resins, halogen-containing compounds have not been used and there have been used organic phosphoric acid esters, for example, monophosphoric acid esters such as triphenyl phosphate, cresyl diphenyl phosphate and tricresyl phosphate, condensed phosphoric acid esters of resorcinol or bisphenol A, a phenol compound and phosphoric acid, etc. However, these resin compositions have problems such as deterioration in heat resistance and physical properties, water absorption at high temperature and high humidity, occurrence of smoke during injection molding, and deposition of flame-retardants onto the mold. Among them, condensed phosphoric acid esters obtained from resorcinol, 2,6-dimethylphenol and phosphoric acid are considered to be less problematic.
Furthermore, as for the flame-retardation of polyphenylene ether resins or mixed resins thereof with styrene resins, resin compositions containing phosphazene compounds such as phenoxyphosphazene as flame-retardants are disclosed in JP-B-3-73590, JP-A-9-71708, JP-A-9-183864, JP-A-11-181429 and WO 00/09518. However, even though these resin compositions are larger in phosphorus content as compared with the above resin compositions containing organic phosphoric acid ester flame-retardants, the former resin compositions are insufficient in flame retardancy and sometimes cause deterioration of electrical characteristics inherent to resins and formation of deposits onto the mold during molding, and thus they are not considered to be effective flame-retardants.
An object of the present invention is to provide a resin composition which contains no halogen-containing compounds, is excellent in heat resistance, mechanical characteristics and electrical characteristics, has substantially no problems such as occurrence of smoke during injection molding and deposition of flame-retardants on the mold, is preferred for environmental health, and has high flame retardancy.
As a result of intensive research conducted by the present inventors in an attempt to attain the above object, it has been found that the above object can be attained by using a resin composition containing a resin composition comprising a polyphenylene ether resin or a polyphenylene ether resin and a polystyrene resin and a specific phosphazene compound. Thus, the present invention has been accomplished.
That is, the present invention relates to the following inventions.
[1] A resin composition containing (A) a resin composition comprising a polyphenylene ether resin or a polyphenylene ether resin and a polystyrene resin and (B) a phosphazene compound having an acid value of less than 0.5.
[2] A resin composition as mentioned in the above [1], wherein the acid value of the phosphazene compound is less than 0.3.
[3] A resin composition as mentioned in the above [1] or [2], wherein the phosphazene compound is a phenoxyphosphazene compound.
[4] A resin composition as mentioned in the above [1] or [2], wherein the phosphazene compound has a cyclic structure.
[5] A resin composition as mentioned in the above [1] or [2], wherein the phosphazene compound is a phenoxyphosphazene compound having a crosslinked structure.